1. Field of Invention
The current invention relates generally to apparatus, systems and methods for transmitting wireless signals. More particularly, the apparatus, systems and methods relate to transmitting wireless information using pulse-position modulation with independently coded and delayed in phase and quadrature components. Specifically, the apparatus, systems and methods provide for transmitting wireless data that is adaptable in response to user needs and propagations conditions in addition to having a low probability of detection (LPD).
2. Description of Related Art
Many prior art LPD systems depend on frequency hopping and direct sequence spreading to achieve LPD on relatively narrowband channels (typically 30 MHz or less). Typically, phase modulation is applied to these signals to modulate data on the carriers. Pulse-position modulation (PPM) is also a well-known technique for modulating data. When combined with relatively short pulses, combining these techniques provide a very high degree of low probability of interference (LPI) while affording the use of easily implementable very short correlators for pulse detection. Other modulation approaches that modulate using direct sequence with frequency hopping typically require much longer correlators requiring higher receiver complexity. A need therefore exists for improved methods and apparatus for communication with a low probability of detection by unintended receivers.